Asian corn borer (ACB), Ostrinia furnacalis Guenee (Lepidoptera: Crambidae) and the rice moth (RM), Corycyra cephalonica Stainton (Lepidoptera: Pyralidae) are economically significant insect pests that threaten the agricultural products worldwide. Trichogramma parasitoids are successfully mass-reared using artificial host eggs, RM, and are often managed by economically important lepidopterous pests, such as ACB in China. Trichogramma ostriniae Pang and Chen (To) and T. dendrolimi Matsumura (Td) (Hymenoptera: Trichogrammatidae) are two important parasitoids of ACB. To determine the influence of interspecific competition between To and Td on their offspring’s emergence. We determine the emergence of wasp progeny from two distinct hosts (ACB and RM eggs) of varying densities (10, 20, 30, and 100) by examining the effect of three distinct oviposition sequences (To-Td, Td-To, and To+Td) by two Trichogramma species. We discovered that the progeny emergence rate of To and Td from the host was substantially influenced by the parasitoid types, host types, oviposition sequences, and host densities, and their two-, three-, and four-factor interactions while investigating the ACB and RM eggs after oviposition. Additionally, the progeny of Td emerged from 10, 20, and 30 ACB host eggs under three oviposition sequences, which was significantly higher than that of ACB eggs of 100 densities. Nevertheless, the optimum emergence rate of Td progeny was also observed in ACB eggs with a density of 100 under all oviposition sequences. The most suitable oviposition sequences for both wasp species are To-Td and Td-To, as they have the highest rate of progeny emergence. The progeny emergence of both Trichogramma species from RM eggs of varying densities was observed to be significantly different. Nevertheless, the most influential density is 100 RM eggs, as a result of the maximal emergence rate of To and Td. Overall, it is concluded that host eggs with a density of 100 are adequate to meet the oviposition requirements of both wasps in all oviposition orders, thereby limiting their interspecific competition. These findings provide insights into optimizing host density and oviposition strategies for mass-rearing Trichogramma species, which can enhance their efficacy in biological control programs. Future research should explore field-level applications to validate these laboratory findings under natural conditions.

In China, the Asian corn borer (ACB), Ostrinia furnacalis (Guenee) (Lepidoptera: Pyralidae), is the most significant economic insect pest of corn, causing losses ranging from six to nine million tons annually by feeding on all parts of maize, including damaging ears and leaves and making tunnels in stems. In China, since the 1970s, the Trichogramma species have extensively mass-reared from factitious hosts to control ACB and support integrated pest management programs. The Trichogramma dendrolimi Matsumura and T. ostriniae Pang and Chen are the most efficient biocontrol agents for controlling ACB among the available Trichogramma species. To evaluate the reproductive success of Trichogramma dendrolimi and T. ostriniae, we assessed the impact of varying parasitoid ratios (5:1, 3:1, 1:1, 1:3, and 1:5 representing T. dendrolimi and T. ostriniae, respectively) on adult offspring emergence and mortality from ACB eggs over multiple generations (from first (F₁) to third (F₃) generations). We discovered that both Trichogramma species’ offspring emergence was significantly influenced by the parasitoid generations, parasitoid ratios, and their interactions. The offspring mortality in both Trichogramma species was significantly affected by parasitoid generations but was not significantly influenced by parasitoid ratios or interaction between parasitoid generations and parasitoid ratios. Furthermore, at parasitoid ratios of 5:1, 3:1, and 1:1, the emergence rate of the F₁ generation of T. dendrolimi was significantly higher compared to the ratios of 1:3 and 1:5. However, in the F₂ generation, the emergence of T. dendrolimi decreased considerably, and no emergence was observed in the F₃ generation. A contrasting trend was observed in the emergence of T. ostriniae offspring. Overall, regardless of the parasitoid ratios, the offspring emergence of T. ostriniae in all three generations was significantly higher than that of T. dendrolimi. After assessing the offspring mortality in our research by dissecting the unhatched eggs, we found an inverse relationship between the T. dendrolimi generations and their mortality across different parasitoid ratios. Notably, mortality exhibited a significant decline with an increasing number of generations. A positive correlation was observed between the number of T. ostriniae generations and their mortality across different parasitoid ratios, indicating that mortality increased with successive generations. Overall, across all parasitoid ratios and generations, the offspring mortality of T. ostriniae was considerably greater than that of T. dendrolimi. These results suggest that mortality is a crucial empirical measure that validates T. ostriniae’s superiority over T. dendrolimi. These findings highlight the importance of selecting suitable parasitoid species when implementing Trichogramma for pest management.

Globally, Spodoptera frugiperda is a major threat to many important crops, including maize, rice, and cotton, causing significant economic damage. To control this invasive pest, environmentally friendly pest control techniques, including pheromone detection and identification of potential molecular targets to disrupt S. frugiperda mating communication, are needed. Female moths biosynthesize pheromones and emit them from the pheromone gland, which significantly depends on the intrinsic factors of the moth. Male S. frugiperda have a sophisticated olfactory circuit on their antennae that recognizes pheromone blends via olfactory receptor neurons (ORNs). With its potential to significantly modify the insect genome, CRISPR/Cas9 offers a revolutionary strategy to control this insect pest. The impairing physiological behaviors and disrupting the S. frugiperda volatile-sensing mechanism are the main potential applications of CRISPR/Ca9 explored in this review. Furthermore, the release of mutant S. frugiperda for their long-term persistence must be integral to the adoption of this technology. Looking forward, CRISPR/Cas9-based gene drive systems have the potential to synergistically target pheromone signaling pathways in S. frugiperda by disrupting pheromone receptors and key biosynthesis genes, thereby effectively blocking intraspecific communication and reproductive success. In conclusion, CRISPR/Cas9 provides an environmentally friendly and revolutionary platform for precise, targeted pest management in S. frugiperda.

The tomato leaf miner, Phthorimaea (Tuta) absoluta, Meyrick 1917 is recognized as a highly destructive pest, causing significant economic losses to crops in both greenhouse and open field environments across four continents: Asia, Africa, Europe, and South America. High genetic homogeneity among populations from various regions and countries indicates significant gene flow between P. absoluta populations, suggesting a lack of geographical barriers to dispersion. Furthermore, P. absoluta has developed resistance to insecticides due to target-site mutations or metabolic resistance, which enable the insect to withstand lethal doses of insecticides. To control this insect pest, the plant-mediated RNA interference (RNAi) is most promising host-induced gene silencing technique, utilized the plant’s machinery to express double-stranded (dsRNA), which triggers the RNAi pathway in P. absoluta. Due to thermal tolerance, the P. absoluta has increased its area of invasion by 600 km per year over 9 years. Female P. absoluta releases pheromones that are recognized by males with a sophisticated olfactory circuit on their antenna. Pheromone binding proteins (PBPs) play a crucial role in mate recognition and attraction, and their expression peaks during courtship, specifically around 6:00 a.m. Given its potential to significantly alter the insect genome, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) offer a revolutionary strategy to control P. absoluta. Furthermore, this pest has developed remarkable adaptations to survive on unfavorable hosts by secreting specific proteins from its salivary glands that detoxify plant defenses. Insecticide resistance is likely the cause of field control failures of P. absoluta. Biological control, sex pheromone traps, and cultural control are the most promising approaches to address insecticide resistance resulting from these failures. Therefore, the implementation of integrated control programs and appropriate resistance management strategies is necessary to keep P. absoluta infestations under economic damage thresholds.

Globally, Trichogramma Westwood (Hymenoptera: Trichogrammatidae) is known as the most effective biological control agent due to its ability to parasitize insect pest eggs. However, identifying an appropriate host is vital for Trichogramma to prosper. Therefore, this study delves into the complex role of semiochemicals in shaping the host-seeking behavior of Trichogramma parasitoids, with a particular focus on their responses to both plant-derived and host-derived cues. The mechanism of semiochemical reception in Trichogramma wasps relies on a highly specialized, sensitive olfactory and gustatory system to locate host eggs and mates. Semiochemicals, which mediate ecological interactions, have been identified as pivotal in influencing the parasitic efficiency of Trichogramma species. Trichogramma’s host-seeking behavior is influenced not solely by ovipositional cues but also by the intrinsic physical attributes of Lepidopteran hosts, such as the scales on the wings and abdomen, which emit semiochemicals capable of eliciting positive chemotactic responses, thereby guiding parasitoids toward optimal sites for oviposition. Furthermore, the interplay between insect-derived and plant-derived chemical cues exhibits a synergistic effect, collectively enhancing the chemotactic attraction of Trichogramma, thereby fine-tuning its host-seeking behavior with greater precision and specificity. This study further underscores Trichogramma’s innate behavioral ability to discriminate between host eggs of varying developmental stages, facilitating the precise identification and selection of the most suitable host for parasitization. Age and experience both make Trichogramma more selective of hosts, but younger parasitoids may take a broader approach to host selection due to their greater life expectancy. Furthermore, the removal of these cues affects their host localization and learning abilities. Associative learning enables Trichogramma to exhibit flexible behaviors, providing them with a selective advantage; allows them to explore various hosts; and reduces environmental uncertainty. Plant structure, host density, and host age are the key factors that significantly influence the foraging and parasitism of Trichogramma. The searching speed of this parasitoid is significantly influenced by temperature. Heat stress increases VOC emissions in plants such as potato via stomatal opening, reducing herbivore attraction and enhancing parasitoid recruitment. Furthermore, air pollution, including CO₂, O₃, and NOx, impairs parasitoid efficiency by disrupting volatile-mediated host location and reducing biological control performance. Trichogramma wasps are generally effective biological control agents, but their success depends on the species used, target pest, crop, release density, and field conditions. Overall, species such as T. ostriniae, T. japonicum, and T. leucaniae show the strongest performance in several crops by increasing parasitism, reducing pest damage, and improving yield. This study highlights the successful integration of semiochemical cues in pest management programs and the effective utilization of Trichogramma in conjunction with entomopathogenic bacteria to control Lepidopteran pests. This approach contributes to the development of more effective pest management strategies, thereby promoting agricultural sustainability.

Diapause is an important seasonal adaptation that enables Trichogramma egg parasitoids to survive unfavorable environmental conditions and maintain synchrony with host availability. Although temperature and photoperiod are established regulators of diapause, plants can influence parasitoid ecology through changes in host availability, volatile emissions, defense responses, host egg quality, and local environmental conditions. This review synthesizes evidence on plant–herbivore–Trichogramma interactions and examines their potential relevance to diapause regulation and biological control. Studies demonstrate that plant species, host-plant phenology, herbivore-induced and oviposition-induced volatiles, and plant defense responses can affect parasitoid host searching and parasitism. Plant-mediated changes in host nutrition and plant architecture also influence parasitoid development, dispersal, and performance, although responses vary among species and environmental conditions. We further review evidence on the regulation of Trichogramma diapause by temperature, photoperiod, maternal effects, metabolic pathways, and population-specific responses, together with recent findings on lipid metabolism, carbohydrate transport, endocrine signaling, and symbiont-associated variation. Importantly, direct experimental evidence linking plant-derived cues to diapause induction remains limited. Climate change may further affect parasitoid–host synchrony by altering thermal conditions, plant development, host phenology, and extreme temperature exposure. Future research should integrate plant chemistry, host egg quality, maternal conditions, and physiological measurements with direct assessments of diapause under realistic environmental conditions. Such studies may improve our understanding of seasonal adaptation and support more reliable Trichogramma-based biological control.